1. Field of the Invention
The invention relates to an unintentional hand movement canceling device installed in, for example a video camera and a digital camera, and an imaging apparatus such as a video camera and a digital camera.
2. Description of the Related Art
A method for detecting a swing component of an image pick-up device, as an example, was presented in the 20th image optics conference (1989) from Matsushita Electric Industrial Co., Ltd. This method is to detect a swing component of an image pick-up device from image information using a motion vector obtained from a representative point matching method described in JP-A No. 61-201581 [H04N7/137] laid open to public on Sep. 6, 1986. In this presentation, a damping coefficient is introduced in a method for canceling an unintentional hand movement based on motion vectors obtained from image information. Besides, 4 detection regions are arranged on a screen image and partial motion vectors are calculated in the respective 4 detection regions.
Description will be given here of a method for canceling an unintentional hand movement based on the obtained partial motion vectors. The average of 4 partial motion vectors or the like is used as each of overall vectors of frames. An integral vector Sn is given by the following equation (1) when an overall motion vector is indicated with Vn;Sn=K·Sn−1+Vn  (1)
In the equation (1), Sn indicates an integral vector in a current frame, Sn−1 an integral vector in the immediately proceeding frame, Vn an overall motion vector and K a damping coefficient of an integral vector. A damping coefficient K of an integral vector K is a decimal less than 1.
By moving a trimming position of a screen image with thus obtained integral vector Sn, an unintentional movement of image due to an unintentional hand movement is corrected. An integral vector Sn, as shown in FIG. 7, expresses a distance to and a direction toward the center Ot of a displayed region (trimming frame 100) from the center O of an image memory (frame memory 15).
Controlling a damping coefficient K can cause a non-corrected residue percent (a frequency characteristic of a swing to be corrected) at a frequency of a swing and a velocity returning a trimming position of an image to the center of an image memory (the velocity is hereinafter referred to as a centering velocity) to be altered. A non-corrected residue percent is defined as a proportion (%) of the amplitude of a swing after the correction, relative to the amplitude of a swing before the correction.
FIG. 19 shows a relationship between a swing frequency [Hz] and a non-corrected residue percent (%) with a damping coefficient K as a parameter.
For example, in a case where K=1.0, a detected movement is perfectly corrected. In a case where K=0.90, a swing of 2 [Hz] is corrected by about 50% and a swing of 5 [Hz] is corrected by about 70%. That is, with a decrease in damping coefficient K, a correction level for a swing in lower frequency band is weakened.
Since a damping coefficient K plays two roles to control a frequency characteristic of a swing to be corrected and a centering velocity, a characteristic cannot be set independently of the other. For example, if a damping coefficient K is reduced with an intention not to correct a swing in low frequency region, a centering velocity increase as a side effect; therefore a problem has arisen that a phenomenon that an image moves in a delayed manner even if a motion of a video camera is stopped becomes conspicuous (the phenomenon is hereinafter referred to as a delayed swing).
To the contrary, if a damping coefficient K is set to 1 so as to perfectly correct a swing in low frequency band, a problem has arisen that no centering occurs and a correction range cannot be secured. A proposal has been offered in JP-A No. 7-23276 on a measure to cope with this problem. In the publication, attention has been paid to the fact that a delayed swing is conspicuous after shooting in panning or tilting and a trimming position of an image is moved toward the center side of an image memory by a predetermined portion of a motion vector during a panning or tilting shooting. However, a problem has arisen that since erroneous detection of a motion vector occurs frequently during shooting in panning or tilting, operability during the shooting in panning or tilting is greatly reduced.